manpages: grammar fixes

Library/Homebrew/cmd/--version.rb

Library/Homebrew/cmd/analytics.rb

Library/Homebrew/cmd/install.rb

Library/Homebrew/cmd/migrate.rb

Library/Homebrew/cmd/missing.rb

Library/Homebrew/cmd/options.rb

Library/Homebrew/cmd/reinstall.rb

Library/Homebrew/cmd/search.rb

Library/Homebrew/cmd/sh.rb

Library/Homebrew/cmd/switch.rb

Library/Homebrew/cmd/tap.rb

Library/Homebrew/cmd/uninstall.rb

Library/Homebrew/cmd/upgrade.rb

Library/Homebrew/cmd/uses.rb

Library/Homebrew/dev-cmd/audit.rb

Library/Homebrew/dev-cmd/prof.rb

Library/Homebrew/dev-cmd/ruby.rb

Library/Homebrew/diagnostic.rb